﻿using System;
using System.IO;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;
using Humanizer;

namespace Artemis.Core;

/// <summary>
///     Represents a plugin prerequisite action that downloads a file
/// </summary>
public class DownloadFileAction : PluginPrerequisiteAction
{
    /// <summary>
    ///     Creates a new instance of a copy folder action
    /// </summary>
    /// <param name="name">The name of the action</param>
    /// <param name="url">The source URL to download</param>
    /// <param name="fileName">The target file to save as (will be created if needed)</param>
    public DownloadFileAction(string name, string url, string fileName) : base(name)
    {
        Url = url ?? throw new ArgumentNullException(nameof(url));
        FileName = fileName ?? throw new ArgumentNullException(nameof(fileName));

        ShowProgressBar = true;
    }

    /// <summary>
    ///     Creates a new instance of a copy folder action
    /// </summary>
    /// <param name="name">The name of the action</param>
    /// <param name="urlFunction">A function returning the URL to download</param>
    /// <param name="fileName">The target file to save as (will be created if needed)</param>
    public DownloadFileAction(string name, Func<Task<string>> urlFunction, string fileName) : base(name)
    {
        UrlFunction = urlFunction ?? throw new ArgumentNullException(nameof(urlFunction));
        FileName = fileName ?? throw new ArgumentNullException(nameof(fileName));

        ShowProgressBar = true;
    }

    /// <summary>
    ///     Gets the source URL to download
    /// </summary>
    public string? Url { get; }

    /// <summary>
    ///     Gets the function returning the URL to download
    /// </summary>
    public Func<Task<string>>? UrlFunction { get; }

    /// <summary>
    ///     Gets the target file to save as (will be created if needed)
    /// </summary>
    public string FileName { get; }

    /// <inheritdoc />
    public override async Task Execute(CancellationToken cancellationToken)
    {
        using HttpClient client = new();
        await using FileStream destinationStream = new(FileName, FileMode.OpenOrCreate);
        string? url = Url;
        if (url is null)
        {
            Status = "Retrieving download URL";
            url = await UrlFunction!();
        }

        void ProgressOnProgressReported(object? sender, EventArgs e)
        {
            if (Progress.ProgressPerSecond != 0)
                Status = $"Downloading {url} - {Progress.ProgressPerSecond.Bytes().Humanize("#.##")}/sec";
            else
                Status = $"Downloading {url}";
        }

        Progress.ProgressReported += ProgressOnProgressReported;

        // Get the http headers first to examine the content length
        using HttpResponseMessage response = await client.GetAsync(url, HttpCompletionOption.ResponseHeadersRead, cancellationToken);
        await using Stream download = await response.Content.ReadAsStreamAsync(cancellationToken);
        long? contentLength = response.Content.Headers.ContentLength;

        // Ignore progress reporting when no progress reporter was 
        // passed or when the content length is unknown
        if (!contentLength.HasValue)
        {
            ProgressIndeterminate = true;
            await download.CopyToAsync(destinationStream, Progress, cancellationToken);
            ProgressIndeterminate = false;
        }
        else
        {
            ProgressIndeterminate = false;
            await download.CopyToAsync(contentLength.Value, destinationStream, Progress, cancellationToken);
        }

        cancellationToken.ThrowIfCancellationRequested();

        Progress.ProgressReported -= ProgressOnProgressReported;
        Progress.Report((1, 1));
        Status = "Finished downloading";
    }
}